I met Gary briefly at the NY Comic Con a few years back when he was a guest there, and while he definitely had that gruff exterior he was known for, overall he was nice, though very business like. He wouldn't personalize autographs, but he would sign stuff and you could take a picture with him which for those of you on my Facebook, I have on there.
The one thing that was really cool that he did when I met him is, someone online before me was taking a real long time getting their camera to work, and Gary had turned to me and said "I'll be with you in a minute, I'm not ignoring you". Which I thought was really nice of him.
He is the second celebrity I've met that has passed away recently (I also had the pleasure of meeting former Muppet Show guest Lynn Redgrave)